Concept:Geometric (cis-trans) isomerism is possible in cyclic compounds when two separate carbon atoms in the ring are each bonded to two different substituent groups. The rigid ring prevents free rotation.
Solution:- A. 1,1-dimethylcyclopropane: Both methyls are on the same carbon. No geometric isomerism possible.
- B. 1,2-dimethylcyclopropane: Carbon-1 is bonded to H and \( \text{CH}_3 \). Carbon-2 is bonded to H and \( \text{CH}_3 \). Because they are on different carbons, the methyls can be on the same side of the ring (cis) or opposite sides (trans). It shows geometric isomerism.
- C & D: Do not have enough substituents on different carbons to exhibit spatial variation relative to a plane.
Why other options are incorrect:The lack of two distinct substituted chiral centers in the ring prevents the formation of distinct cis and trans configurations.
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